It is generally useful to provide an electronic means to modulate the intensity of optical radiation. Applications of such modulators include, for example, spatial light modulators, optical displays, and other similar applications. Examples of light modulators include liquid crystal, electrochromic, electromechanical, Bragg, and other technologies. Liquid crystal modulators rely on rotating a plane of polarization of incident light to modulate light. Electrochromic modulators inject ions into (or out of) a material such that the material changes from being optically transparent to optically absorbing. A back reflector (e.g., a metal mirror) is placed behind this material so that light may either be reflected by the reflector or absorbed by the electrochromic layer. The mirror is perforated so that ions may pass through the mirror. Depending on the application, moving the ions may require a large amount of energy and the rate of change is relatively slow (around 1 Hz).
An electrophoretic modulator is another type of light modulator. A typical electrophoretic modulator uses two differently charged particles of two different colors. An electric force is applied to the particles to cause the particles of one color to move toward a viewing surface and particles of the other color to move away from the viewing surface. By alternating the electric force the color of the viewing surface may alternate between the two colors.